M6 or M5

[nathancates]

Looking at a 2020 t23 with the m5 motor in it. I have had the m6 motor in another boat. Is the m5 worth it or should I find a m6

[ahopkins22LSV]

It all comes down to elevation, transmission ratio, prop and intended use. It’s going to be a very fine line in that boat. I honestly don’t know what the transmission ratio or prop is in the T23 but if it’s 2:1 with the 17” prop and you aren’t looking to absolutely slam the boat and are at sea level then it will probably be fine. If not, then you will probably not be happy with the performance, especially since you have already had the M6

[wdr]

After over 300 hours with the M5 in my ‘19 23 LSV I have to rave about the fuel savings in comparison to my 2010, 350 Monsoon in that LSV. Especially considering the weight difference between the 2. That being said I primarily surf and ordered the 2773, 15x13 on it. Full ballast, pnp and max wedge no problems, at 11.2 mph but @ 3800 rpm. Kind of high for my liking. I haven’t tried the 2249 so I can’t comment on the performance. With my current set up I would be bouncing off the rev limiter trying to wakeboard with max MLS alone and wedge position 2. Given the choice I would go with the M6 for the myriad of reasons that most big engine fan boys and practical people give. Especially with a 17” prop which should also give you plenty of wiggle room to reprop in either direction should you need or choose to. I tired a 16 x 15 on my M5 for a couple weekends last year and I am definitely getting one soon. JM2C

[dlb]

I would look for one with a M6, no woulda, coulda, shoulda…..

My 23LSV has a M6, love it.  Never had a power issue, 11 folks surfing and wakeboarding or just 2 or 3.  

[klntime]

Here's my take with 2021 lsv 23 with M5. 

i would agree with other posts about elevation, prop size, trans ratio etc. factoring into a decision.

Personally, I have zero issues or complaints with the m5 at basically sea fully ballasted (hard tanks and plug n play 100%), wedge typically around 3, 500lbs of additional lead and a crew of 4-8 people (a few of those being kids)  This is running an aggressive 17" torque prop.  Surfing RPM's around 3600 and wakeboarding with this same setup is a bit over 3900 rpms.

With that said, If i had to travel far to my riding spot and wanted to get their faster having the M6 with possibly a less aggressive prop would definitely be something I would consider because you will be spinning fairly high RPM's running over 30mph etc.  Not an issue for me, my riding spot basically starts at my pier and even when I'm in more of a hurry rarely cruise over 25mph anyway.

So for the way I use the boat the M5 works fine never noticed a lack of power.  However, in many circumstance  (elevation, cruising speed, rpm- concerns, huge crew sizes) I could see the M6 being a better fit.

Bottom line, if I was ordering brand new from factory i would probably get the M6,  My boat was a stock boat with the M5... with that said I don't have any complaints, nor does anyone who has driven my boat fully loaded - The Lift on the PW really helps you get on plane fairly fast.  In fact, a good buddy just purchased a 2022 23 lsv with the same M5 after seeing how it performed in my boat.

I can also say the M5 seems to performs better in the 23 lsv (heavier boat) than my 330 monsoon did in an axis T22.

Hope that gives you a little insight.

 

[nathancates]

Thanks for all the responses. 

[MikeR397]

Bumping this for opinions on a m5 vs m6 in a T220. Dealer insists there is no need (Michigan) for an m6 in the 22ft T220, and the m5 will never be underpowered. He also said the top speeds would be similar either way even with a speed prop option right around 40mph. 
 

I’m always of the “go big or go home” for engines and it’s only around $5k to upgrade. The bigger issue is there is an in stock 2023 T220 that might end up being a lot better deal/discount than a 2024 order given current supply issues of boats and it’s essentially the spec I otherwise would custom order except it only has the m5. 
 

I presume both m5 and m6 take 89 octane? Is consumption much worse on the m6 for the surfing? I don’t really care unless it’s a massive difference. 

Edited August 13, 2023 by MikeR397

[BlindSquirrel]

Judging by your writing, there is no question you will only be happy with the m6. If you get the one in stock, you’ll always have the “what if” or “I knew it” feeling. In your case the saying “pay more and once cry once” is spot on. 

[NWBU]

1 hour ago, MikeR397 said:

I presume both m5 and m6 take 89 octane? Is consumption much worse on the m6 for the surfing? I don’t really care unless it’s a massive difference. 

I’ve run every M6 on 87 octane and it’s a very efficient engine. I don’t have any comparison to the M5 though since the one time Malibu put an M5 into the boat I ordered with an M6, I refused delivery because of that.

FWIW, my sea level dealer won’t order the M5 for their stock boats, but they will option up the trailers with 18s. Shows their perspective of what the market values.

[CaptainMorgan]

2 hours ago, MikeR397 said:

Bumping this for opinions on a m5 vs m6 in a T220. Dealer insists there is no need (Michigan) for an m6 in the 22ft T220, and the m5 will never be underpowered. He also said the top speeds would be similar either way even with a speed prop option right around 40mph. 
 

I’m always of the “go big or go home” for engines and it’s only around $5k to upgrade. The bigger issue is there is an in stock 2023 T220 that might end up being a lot better deal/discount than a 2024 order given current supply issues of boats and it’s essentially the spec I otherwise would custom order except it only has the m5. 
 

I presume both m5 and m6 take 89 octane? Is consumption much worse on the m6 for the surfing? I don’t really care unless it’s a massive difference. 

i'm probably in the minority, but unless you are wakeboarding heavy, I bet the M5 is fine for surfing-focused use on a 22ft boat (if serious wakeboarding get the M6). 

But to @NWBU's point, know any $$ savings now will also be reflected in a lower tradein/resale value down the road too. If keeping for 10yrs, who cares.  But if looking to upgrade in a couple years, i'd be sure you're saving a good bit now.  (And i personally think top speed is irrelevant, kids will smile at 37mph and 40mph equally wide... )

For perspective, i have an A24 (bought end of season off the lot a few years ago after not much research and having never heard of TMC...) but it has the 409 vs the 450 -- saved me money up front but if i tried to sell i'm sure some buyers would look right past it for that reason alone.  Frankly my 24fter does great surfing heavy with that 'small' engine at sea level (remember, an M6 at a few thousand feet performs like an M5 at sea level).  The only times i can tell its stretched to its limit is if i cared to wakeboard at max ballast -- mine can (with Wedge Lift mode) but just barely and we don't wakeboard anyway (again, A24 is a much larger/heavier boat). 

i bet if you didn't know the M6 existed you'd use/love the boat with an M5 and never think twice  ....but you do know its an option, so depends if the discount is enough in your eyes to justify buying now and being done with the search. 

[Swatski]

I got a leftover M5 dealer special 2022 23 lsv (we bought it in late Fall 2022), it came with everything I wanted and nothing I didn't want EXCEPT it had the M5, I would had wanted M6. I was concerned but took the risk. Glad I did. 

I feel there is so much misinfo about the M5 vs M6 choices. Based on my experience the M5 performs great in a 23 lsv at least below 1,000ft and would do great in any similar malibu/axis with a 2:1 transmission ratio. If I were on Lake Powell I would want LT4. 

With 50+ hours now (we are very busy and have other boats) after propeller change (we now run w/a big 2805 17x17) the boat runs awesome. we mostly surf, full ballast + the largest pnp bags + 500lbs lead in the bow/mid w/small or moderate crew, wedge at 3-4, speeds 10.8-11.2, running barely over 3,000RPM sippin fuel, top speed is over 40 

I don;t wakeboard anymore but can get to 30+ mph fully ballasted no problem if wanted to. 

With the factory equipped "torque" prop (16.5x14.5 or so) we had 12 adults and ran hard, the boat would do anything, I switched the porp to lower the RPM and love it how quiet it is now. 

[CaptainMorgan]

5 hours ago, Swatski said:

I feel there is so much misinfo about the M5 vs M6 choices. Based on my experience the M5 performs great in a 23 lsv at least below 1,000ft and would do great in any similar malibu/axis with a 2:1 transmission ratio.

anyone know if T220 has the 2:1?  i see it has a 27" draft so that means 15" prop but not sure about transmission.  either way, just means you'd have a different 'best' prop.

[23LSVOwner]

Personally I would go with the M6 minimum, if for nothing else other than the resale value.

Also, I do not know a single person who has complained wishing they had gotten the smaller engine.

[Swatski]

1 hour ago, 23LSVOwner said:

Personally I would go with the M6 minimum, if for nothing else other than the resale value.

Also, I do not know a single person who has complained wishing they had gotten the smaller engine.

It was also my intention to go with the M6. But, a deal is a deal if you find one that's so appealing it is hard to pass. Resale value? I'll just roll my discount into the next sale/purchase but I like the boat enough it's going to be with us for a while. In my thirty year boating career I'm also becoming more and more happy with a "it's good enough" approach. In this context, I have not yet found M5 lacking in any areas of performance of interest to me. 

One possible advantage of the M5 is its apparently higher tolerance for low octane gas, and generally s***ty marina fuel (if/where applicable). In my case that is actually quite reassuring. In general, gasoline does not age well when sitting and premium can quickly become non-premium which is the case on my lake. Pulling the boat out every time I need to refuel is not appealing to me. 

Another advantage of M5? it's big one: my Malibu/Axis dealer mechanic loves those. He tells me the M5s are easier to work on due to being significantly smaller w/more room in the compartment. He cringes on the mere mention of LT4. That's a consideration if you view your purchase as "time on the water" (happy mechanic willing to service my Bu is a wonderful thing). 

Not sure what's beyond M6 - if M6 is "the minimum".  the LT4 is a huge PIA and not something I would opt for in 23/24 or even 25 unless I was lucky enough to boat at high altitude all the time. 

[ahopkins22LSV]

15 hours ago, MikeR397 said:

Bumping this for opinions on a m5 vs m6 in a T220. Dealer insists there is no need (Michigan) for an m6 in the 22ft T220, and the m5 will never be underpowered. He also said the top speeds would be similar either way even with a speed prop option right around 40mph. 
 

I’m always of the “go big or go home” for engines and it’s only around $5k to upgrade. The bigger issue is there is an in stock 2023 T220 that might end up being a lot better deal/discount than a 2024 order given current supply issues of boats and it’s essentially the spec I otherwise would custom order except it only has the m5. 
 

I presume both m5 and m6 take 89 octane? Is consumption much worse on the m6 for the surfing? I don’t really care unless it’s a massive difference. 

@Raimie has a T220 with the M5 in it which is probably why the dealer is stating it is perfectly fine. She has had no issues with it. I also have the M5 in our 22LSV and we have no issues.

[dizzygti]

1 hour ago, Swatski said:

One possible advantage of the M5 is its apparently higher tolerance for low octane gas, and generally s***ty marina fuel (if/where applicable). In my case that is actually quite reassuring. In general, gasoline does not age well when sitting and premium can quickly become non-premium which is the case on my lake. Pulling the boat out every time I need to refuel is not appealing to me. 

Another advantage of M5? it's big one: my Malibu/Axis dealer mechanic loves those. He tells me the M5s are easier to work on due to being significantly smaller w/more room in the compartment. He cringes on the mere mention of LT4. That's a consideration if you view your purchase as "time on the water" (happy mechanic willing to service my Bu is a wonderful thing). 

 

Apparent tolerance?  Where are you getting this from and why do you keep repeating it?    And aren't the M5 and M6 physically the same size?   Sure the LT4 had a big ole charger and heat exchangers on top of it, but the NA motors should be same dimensions.  

[UWSkier]

20 minutes ago, dizzygti said:

Apparent tolerance?  Where are you getting this from and why do you keep repeating it?    And aren't the M5 and M6 physically the same size?   Sure the LT4 had a big ole charger and heat exchangers on top of it, but the NA motors should be same dimensions.  

Tolerance for poor fuel usually means lower compression ratio, but both the M5 and M6 are 11:1, so yeah, not sure why there'd be a difference.

[mrothwell]

Just out of curiosity, how does the M5 specs compare to the old Monsoon 340?

 

[PNWoke]

4 minutes ago, mrothwell said:

Just out of curiosity, how does the M5 specs compare to the old Monsoon 340?

 

Not sure exactly.  But I was told by a dealer that my 409SS is pretty close in performance to the current M5 model.  I don’t know if that means they use the L96 block or of the M5 uses the current GM HD truck block.    

[bcoppess23]

6 minutes ago, PNWoke said:

Not sure exactly.  But I was told by a dealer that my 409SS is pretty close in performance to the current M5 model.  I don’t know if that means they use the L96 block or of the M5 uses the current GM HD truck block.    

The M5 is 5.3l motor and I do not recall that being an option on the HD truck.  M6 is 6.2l and the current HD gasser is 6.6l.

[Swatski]

2 hours ago, dizzygti said:

Apparent tolerance?  Where are you getting this from and why do you keep repeating it?    And aren't the M5 and M6 physically the same size?   Sure the LT4 had a big ole charger and heat exchangers on top of it, but the NA motors should be same dimensions.  

no, the M5 and M6 are not the same size. 

 

 

As far as compression and octane, as I posted in another thread:

" Here is what I see w/rudimentary search of the subject (the GM model #s LS/LH/LQ etc. would remove any uncertainty):

5.3 (3rd gen): Compression Ratio: 9.5:1 – 9.9:1 (https://chevytrucks.org/ultimate-5-3-vortec-engine-guide/)

6.2 (4th gen): Compression ratio: 11.5:1 (https://gmauthority.com/blog/gm/gm-engines/lt1/) "

 

and

 

" There are a dozen variations on the LS-based 3rd (M5?) and 4th (M6?) generation motors - which model # is M5di and M6di?

the higher the compression ratio, the higher the susceptibility to knock with more volatile low octane fuel. It's that simple. 

With low octane there is very little safety margin in a high-compression engine and the knock sensors and the ECU adjusts ignition/ fuel mixture to eliminate knock. If the M6 has higher compression it will adjust more (than M5) to compensate. "

Edited August 14, 2023 by Swatski

[Swatski]

1 hour ago, UWSkier said:

Tolerance for poor fuel usually means lower compression ratio, but both the M5 and M6 are 11:1, so yeah, not sure why there'd be a difference.

may be, may be not. 

GM 5.3 and 6.2 small blocks are a generation apart and not the same compression, so there is that

[PNWoke]

If you’re pulling the 11:1 ratio off the Malibu/monsoon owners manual then consider that it’s probably not exactly 100% accurate.  Both my indmar and Malibu manuals had quite a few errors including recommending the wrong spark plugs.  I called indmar and they acknowledged that often the manuals are created just by updating from old manuals and often information gets carried over from past gens erroneously.  Also the manuals are generalized across all of the options for those years.  My manual covered the 350, 409ss, and LS3.  

[dizzygti]

27 minutes ago, Swatski said:

no, the M5 and M6 are not the same size. 

 

 

As far as compression and octane, as I posted in another thread:

" Here is what I see w/rudimentary search of the subject (the GM model #s LS/LH/LQ etc. would remove any uncertainty):

5.3 (3rd gen): Compression Ratio: 9.5:1 – 9.9:1 (https://chevytrucks.org/ultimate-5-3-vortec-engine-guide/)

6.2 (4th gen): Compression ratio: 11.5:1 (https://gmauthority.com/blog/gm/gm-engines/lt1/) "

 

and

 

" There are a dozen variations on the LS-based 3rd (M5?) and 4th (M6?) generation motors - which model # is M5di and M5di?

the higher the compression ratio, the higher the susceptibility to knock with more volatile low octane fuel. It's that simple. 

With low octane there is very little safety margin in a high-compression engine and the knock sensors and the ECU adjusts ignition/ fuel mixture to eliminate knock. If the M6 has higher compression it will adjust more (than M5) to compensate. "

They have the same bore spacing.   The blocks are the same size, and they use the same crankshaft.   Only the bore size differs.   GM trucks /= Malibu boats.  Page 82 of Malibu owner's manual states: "The minimum octane requirement for a M-Series engine  is 87 (R+M)/2."    Stop assuming the M5 has different compression, because it doesn't, and your concern goes away.  

[dizzygti]

14 minutes ago, PNWoke said:

If you’re pulling the 11:1 ratio off the Malibu/monsoon owners manual then consider that it’s probably not exactly 100% accurate.  Both my indmar and Malibu manuals had quite a few errors including recommending the wrong spark plugs.  I called indmar and they acknowledged that often the manuals are created just by updating from old manuals and often information gets carried over from past gens erroneously.  Also the manuals are generalized across all of the options for those years.  My manual covered the 350, 409ss, and LS3.  

Ok, but the M5, M6, and LT4 were all new at the time of publication.....so....